The present disclosure generally relates to the fabrication of semiconductor devices. In particular, this disclosure relates to the creation of metal interconnect structures within a dielectric layer of an integrated circuit (IC).
An IC, also known as a “microchip,” silicon or computer “chip,” is a specially prepared piece of silicon, or other semiconductor material, into which a complex electronic circuit is etched and formed using a photolithographic process. IC types can include computer processors, memory, analog, and customizable devices. ICs can be relatively fragile, and therefore are often mounted on and/or surrounded by a protective, supportive ceramic or plastic package. Electrical connections to the chip can be provided through metal contacts, which can include pins or solder balls located on the exterior of the chip package.
Galvanic or bimetallic corrosion is an electrochemical process in which one metal preferentially corrodes when in electrical contact, in the presence of an electrolyte, with a dissimilar metal. Dissimilar metals and alloys have different standard electrode potentials, and when two or more dissimilar metals are brought into electrical contact in the presence of an electrolyte, one metal acts as an anode and the other as a cathode. If the electrolyte contains only metal ions that are not easily reduced, the cathode reaction is reduction of dissolved H+ to H2 or O2 to OH−. The electropotential difference between the reactions at the two electrodes is the driving force for an accelerated corrosive attack on the anode metal, which dissolves into the electrolyte. This electropotential difference leads to the acceleration of the anode metal corrosion and the inhibition of the cathode metal corrosion.